Rare Gastric Submucosal Mass: Inflammatory Myoblastic Tumor

Abstract

A 51-year-old man was admitted with a 1-month history of intermittent fever up to 37.8 °C. The fever was not alleviated by antibiotics or antivirus drug. He had no past history of serious illness, operation or hospitalization. Erythrocyte sedimentation rate and C-reactive protein were elevated at 120mm/hr and 106 mg/L, respectively. Other blood tests were within normal limits. Endoscopy revealed a protruding mass situated on the lesser curvature of distal gastric body, near the angular incisures. Endoscopic ultrasound showed an oval hypo echoic mass, 33mm×17mm in size, arising from the muscular is pretrial layer (Figure 1). Abdominal computed tomography scan demonstrated a strongly enhancing mass in the posterior wall of gastric body, approximately 3.4cm in the maximal diameter (Figure 2), which was associated with a sub mucosal lesion such as gastrointestinal stromal tumor, gastric glom us tumor and neuroendocrine tumor. The patient underwent local tumor excision. The cut surface of mass was grayish gelatinous texture (Figure 3). Microscopically, the tumor cells were characterized by proliferation of spindle-shaped atypical my fibroblastic cells and chronic inflammatory cells including plasma cells and lymphocytes (Supple-Figure). Inflammatory Myoblastic tumor (IMT) was further diagnosed by immunohistochemistry, which showed positive staining for desman and smooth muscle actin and was negative for CD117, CD34, and S-100. Lymph nodes tested negative for tumor. The preoperative fever disappeared and did not recur in the postoperative course.